Author Topic: Building a Modern Pneumatic Airgun  (Read 129162 times)

Offline JimM

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Re: Building a Modern Pneumatic Airgun
« Reply #25 on: November 11, 2010, 03:40:41 PM »
Great work there Stot, if the rest turns out as well as the parts so far it's going to be a beauty. Will you be making the stock as well or just the mechanicals?

Cheers

Jim
(a HW80K owner)
Location: Chessington, Surrey

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #26 on: November 12, 2010, 04:50:58 AM »
Great work there Stot, if the rest turns out as well as the parts so far it's going to be a beauty. Will you be making the stock as well or just the mechanicals?

Cheers

Jim
(a HW80K owner)

Not for these one.  I bought 2 stocks of ebay for 9 each posted so if they will work ill use those first.  :thumbup:

Cheers
Stot
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Offline Stot

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Update 5 - Valve Plugs
« Reply #27 on: November 12, 2010, 05:24:04 AM »
Right next up I made the plugs for the valves.  They are threaded brass plugs with a stub to locate the valve spring on, a slot to screw it in and holes for airways.

I started off trying to make them all as one piece then parting off but had a little mishap when I was chamfering the edges for threading and snapped off 3 of them so ended up making them as 2 pairs.
:doh:
There are some milling operations here to cut the slot and drill the holes but I came up with a way to do the lot on the lathe.   The holes were easy, use the 4 jaw chuck and mount the parts off center to drill the holes.   Other than in future using a center drill to start them this worked well.

The slot however slightly more difficult, you could mount an end mill or slitting saw in the lathe, then mount the part on the cross slide and cut the slot, but I have a Unimat SL, So I made a stand for it out of an old indicator stand and clamped it to my cross slide.   Lined up the slitting saw in it with the lathe center line and used the lathe feeds to cut my slot.  :borg:  I can use this as a toolpost grinder in future too.  :ddb:

So below pics showed that I..

  • Turned down the brass bar to major thread diameter and cut recesses with my parting tool.
  • Chamfered the edges for threading.
  • Broke it..  So chucked it up to do just 2 of them./
  • Threaded the bar.
  • Ground an edge on the bottom of an old hacksaw blade and parted off each one, wasting as little as possible.
  • Made the other two the same way.
  • Mounted each one in the lathe to face them off and clean them up.
  • Set up my Unimat SL head on the cross slide.
  • Used an end mill mounted in the chuck to set my slitting saw to center line.
  • Cut the slots.
  • Changed to the 4 jaw chuck and mounted the part off center for hole drilling.
  • Drilled the holes. (I'd use a center drill to start them next time as one slipped)

Other than cleaning up with a needle file thats it.   The last picture is the first attempt at these which I wasnt happy with.  The slitting saw arbour was slipping in the chuck so they all went off center.  Although they would be functional, they arent 'A Game' stuff, so rejected for these rifles.  :dremel:



































Cheers
Stot
« Last Edit: November 28, 2010, 09:47:56 AM by Stot »
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Offline Stot

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Update 6 - Inlet Valve Internals
« Reply #28 on: November 15, 2010, 06:45:01 AM »
Two updates today from the weekend.

First up I made the air inlet valve internals.  Very simple one way valves with an o-ring seal.  Only bit im not making is the O-Ring.  :borg:

So below I,
  • Chucked up some stock and turned it to fit inside the valve housing.
  • Turned a section to slip inside the through-hole in the valve housing.
  • Parted off and flipped it around in the chuck.
  • Turned the spring guide end. That part is done.
  • Mounted a suitable bar in the lathe to make the size of spring I wanted.  pinch the music wire in the chuck and start hand cranking the chuck.
  • After a couple of turns to get a spring started, engage the half-nut to set the carriage moving at the spring TPI youre after and turn for desired length of spring.  Disengage half-nut and finish the spring with a couple of turns.
  • Clean the springs up and all parts ready for assembley.

















Tested these and they hold 30bar pressure overnight so at the moment, jobs a goodun.   :beer:

Cheers
Stot
« Last Edit: November 28, 2010, 09:47:17 AM by Stot »
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Offline Stot

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Update 7 - Poppet Valve Internals
« Reply #29 on: November 15, 2010, 08:17:18 AM »
Ok so part 2-2, the Poppet valve internals.

I am veering slightly from the book valve design that uses a flat seated valve.  I am going to use a tapered valve seat and seal which I feel has better redundancy in the design, and has better air flow characteristics.

So,
  • Cut the valve seat into the valve body.
  • Chucked up some Delrin to make the valve seal.
  • Drilled a hole to thread onto the valve stem.
  • Parted off using a 60 degree tool bit.
  • 2 valve seals.
  • Chucked up some bar to cut the valve stem.  This is a bit big, but I had it around so it will do. :D
  • Turned it down to a 'go' fit to the valve housing then polished it up.
  • Turned down to make a thread for the seal to go on. Threaded.
  • Parted off and mounted in the chuck again.
  • Threaded the Delrin seal onto the rod.
  • Cleaned up the seal face and cut the spring guide onto the back of it.
  • Assembled the valve with a spring made the same as the one above.







































Filled to 70bar overnight just to see it held pressure.  No problems.   :headbang:

Cheers
Stot
« Last Edit: November 28, 2010, 09:46:26 AM by Stot »
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Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #30 on: November 15, 2010, 11:36:14 AM »
Nice to see some one else in to it.
Havent made any for close on 8 years the laws have changed since. The last ones been on hold ever since but essentially made and lingering around some where.
I wouldnt pay any attention to those books, make it up as you go on and you will learn a lot more than any book to date has to offer.

Looking at it, yes it will work but know you will have trouble with that knock open valve. It drove me round the bend 19 years ago trying to self regulate them valves to acceptable limits. In the end made a regulator similar to the late Mick Dawes design often copied and used in other rifles, Anchutz, BSA, ISP and more.

Pressure tested the tube? 1 1/2 times the operating pressure, shame manufacturers dont do that. No reason to doubt your threads wont hold the pressure but its a safety thing!
Can do it with a modded grease gun and clock, fill air tube with water and pump oil in. 1/8"BSP off the shelf hydraulic will shear at 6300psi.

Why aint you making the stock, small bore tube easy and quick.

Heres an early one that packed up in 2005 used three times a week for 12 years.
http://pic20.picturetrail.com/VOL15/728921/1313294/111432614.jpg
Number 7 1996 rotting away http://pic20.picturetrail.com/VOL15/728921/1313294/15295231.jpg

Last one been on hold since Maarch 2004
http://pic20.picturetrail.com/VOL15/728921/1723145/20512931.jpg
http://pic20.picturetrail.com/VOL15/728921/1723145/20513282.jpg
http://pic20.picturetrail.com/VOL15/728921/1723145/21294937.jpg
http://pic20.picturetrail.com/VOL15/728921/1723145/303431797.jpg
Tube is done not shown, just needs O rings and a lot of faffing about to get it right, then theres the making of the stock, easy.

Theres over 6k's worth here. http://pic20.picturetrail.com/VOL15/728921/8449063/360648667.jpg
« Last Edit: November 15, 2010, 03:48:06 PM by Jonny »

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #31 on: November 15, 2010, 11:37:28 AM »
Actually you can up that a 1000+ theres a March scope on it at the moment.

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #32 on: November 15, 2010, 02:58:47 PM »
The test fill to 70bar was just to see if it would seal but yeah ill pressure test it up to 4-500 bar depending on if I regulate it.  I have regulated my BSA Ultra and love the consistency and it sure would make spring balancing easier...  :lol:

Nice stuff there right at the pioneering end of modern PCPs.  :smart: Impressive FT rig, not my cuppa though, I'm more into practical hunting stuff.  Love my Phoenix, it looks like a stalking rifle and does the job really well.   The stocks I got off Ebay are going to work really well I think, especially as these are just for my own use. They are comfortable for me and just need re-inletting but thats the easy bit.



Cheers
Stot
« Last Edit: November 15, 2010, 03:47:25 PM by Stot »
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Offline JimM

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Re: Building a Modern Pneumatic Airgun
« Reply #33 on: November 15, 2010, 03:40:01 PM »
Location: Chessington, Surrey

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #34 on: November 15, 2010, 03:47:16 PM »
Would be bordering semi bullpup with that stock, usually rear of action is level at the front of pistol grip.
My first ones the rear end hammer to valve was short, really short then set back a bit, thumbhole under trigger block.
Sussed out short stroking back in 92 without side effects- 1.4mm hammer stroke, presentable at 2.8mm. To date no one sussed even now only running 5.5mm.

The fill probe first used by Titan in 93 a reverseal of what i came up with on first two guns plus Stalker, now used on AA what did they ever design.

Any ideas for a trigger :bang:
Single stage real easy, two stage very very hard to get right.
Did a semi bullpup in 95 in stainless G316 S11, trigger block 13" long no linkages and long first stage returning. Could hold in vice blow on blade and it would go off.

Its what i was good at back then because i didnt read from a book and understood how things should work and be made, a book cant teach that.

Offline Jonny

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Re: Building a Modern Pneumatic Airgun
« Reply #35 on: November 15, 2010, 03:57:38 PM »
Yes typo that pound sign, duly altered.
Serious dosh not for use down the cut, scope was near 1200 6 years ago but can pay 3k now with mounts.

First air rifles made cost me around 20 for the wood, 20 butt pad, 6 hydraulic tube, 5 springs and screws, free barrel and approx 15 of ancilliary items.

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #36 on: November 15, 2010, 04:00:41 PM »
I have an idea for an adjustable 2 stage trigger but not sure on it at the moment I need to do some testing to see if it will work as I hope.

Your current gun reminds me of the Alros Trailsman TDR.  Trigger on that was very... agricultural and is what gave me the idea for the trigger i'm planning as I wanted to replace the trigger on it.

Quote
Did a semi bullpup in 95 in stainless G316 S11, trigger block 13" long no linkages and long first stage returning. Could hold in vice blow on blade and it would go off.

That sounds similar to what I have in mind only twice as long, but I'll leave the details until I'm there though, just incase It fails miserably and I change it completely. :D

Cheers
Stot
« Last Edit: November 15, 2010, 04:03:29 PM by Stot »
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #37 on: November 19, 2010, 11:16:11 AM »
Just found this thread and have read through it with interest.  I have both of Buckley's books, but in the end, I built a bulk CO2 air rifle based more on the Stealth layout.  I like your poppet valve approach better than Buckley's.  What's the diameter of the delrin valve head?  Also, what size thread did you use on the valve stem?

Thx...
Chuck

Here's a link to my CO2 air rifle...

http://www.youtube.com/watch?v=1n-EXv5lLbE

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #38 on: November 19, 2010, 04:46:59 PM »
I like your poppet valve approach better than Buckley's.  What's the diameter of the delrin valve head?  Also, what size thread did you use on the valve stem?

Hi Chuck,

I seen your video before actually when I was first looking at building something its a great setup.  :clap:  Great thing about the book design is it should run nicely on CO2 with just a little adjustment, especially with a 24" barrel.  :thumbup:

The book doesn't cover the poppet valve head too well in the schematics.  Theres no sizes or anything for making the seal and cap.  Also looking at the recess in the pin that aids airflow in the schematics, it looks like its in the wrong place, i.e. the edge of the recess is in line with the transfer port with the pin is at rest, rather than when the valve is open.  So I decided to do it my way.

The poppet valve head is 9mm-6.5mm @ 60 degrees.  I threaded the valve pin M4 and left a shoulder on it then self tapped it into a 3mm hole in the delrin.   I had to re-design the valve pin to accommodate the tapered seat but it seals real nice.

Haven't done anything on it this week, Got to get the hammer tube done over the weekend and im coing to case harden the valve pins too.  :coffee:

Cheers
Stot

« Last Edit: November 19, 2010, 05:35:37 PM by Stot »
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Offline Stot

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Update 8 - Hammers
« Reply #39 on: November 22, 2010, 05:33:01 PM »
Well a few days since my last update but I'm at a stage where parts of the design for one part is dependant on the design and position of another part.

As standard the book rifle has seperate hammer cocking handle and bolt handle.  I want the rifles to be bolt cocking only so I have had to redesign the breech block, the bolt, the hammer and the hammer tube slightly.  Also roughed up the trigger assembley so now I have positions of all the areas I have to mill on the hammer tube and breech.

I threaded the hammer tube to take fit the valve the same way I did the air tubes and what this all means is the last parts I have to turn are the bolt and handle, the hammer and the hammer tube end cap.  The rest is milling operations so Ill get the turning out of the way then set the lathe
up for milling and do the lot.

First up was the hammers.

  • Threaded the hammer tubes to fit on the valves.
  • Faced off and turned down some stock to slip fit the hammer tube.
  • Center drilled then drilled through the stock.
  • Bored out a recess for the hammer spring to guide in.
  • Turned the stock around and turned the other end down under size.  This is because the shoulder that is left will be the sear.
  • Polished it up, hammer done.



























Ill case harden these too so the sears work nicely.   :thumbup:

Cheers
Stot
« Last Edit: November 28, 2010, 09:45:25 AM by Stot »
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Offline Dean W

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Re: Building a Modern Pneumatic Airgun
« Reply #40 on: November 22, 2010, 11:49:51 PM »
Great thread you have here, Stot.  I've thought about building an air rifle a few times, but it always gets
pushed aside for engine or shop projects.  Being a long time shooter, both air and firearms, this build has a
lot of interest for me.  Maybe I'll get to it someday.  Glad you are posting up your progress.

Dean
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Offline Stot

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Update 9 - Pellet Probe Bolts
« Reply #41 on: November 25, 2010, 03:13:54 AM »
Another update.  I made one of the bolts/pellet probe.   I wasnt sure wether to make this out of steel or brass.  Steel would be easier for me, I hate machining brass because I end up pulling splinters out of every appendage for days.  :bang:

I had a scrap of brass big enough, and I think it will accent well with the brass valves and trigger, so I bit the bullet and made it from that.  I did wear some nitrile gloves which helped a lot with the splinters.  :thumbup:

The pellet probes are calibre specific, my rifles will be .22 to start with although I may convert one to .177 later. I can turn a .22 probe down to .177, but not the other way so I'll make them both .22 for now.

Very simple turning operations to make the bolt, but it will be cross drilled for a pin to be screwed into when I'm set up for milling.  The bolt handle can be put on either side in my re-design for a fully ambedextrous(sp?) operation.

  • Chucked up the rough brass I had and turned it down to the same diameter as my barrels.  This means I just need to drill one size hole through the breech block.
  • Turned it around, parted it off and turned it down to just under the barrel bore size.
  • Turned down the tip of the probe that will push the pellet past the barrel transfer port.
  • Polished it up a bit.
  • Turned it around again and made a threadded hole for the bolt handle bolt.

























You can see where ive marked for an o-ring on the end of the probe to seal the barrel when cocked, but Im not sure what o-ring ill be using yet so ill cut the groove when I have the o-ring.

Cheers
Stot
« Last Edit: November 28, 2010, 09:44:55 AM by Stot »
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Offline Stot

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Update 10 - Case Hardening Hammers
« Reply #42 on: November 28, 2010, 09:42:27 AM »
This week I ar bin mostly turnin'.   Well that and a little case hardnening.

The ridge on the hammers makes up part of the sears in the trigger, so it makes sense to harden them so they don't wear easily.  The steel I had was EN1A So case hardening it is the only way to go.  Also the tip of the hammer is an adjustable screw and as this is what will take the brunt of the impact force so hardening the threads is sensible too.

I wasnt sure if I was going to get the hammers hot enough with just a propane/butane blow torch but it came up a very nice cherry red.  I cant file or scribe them when done so jobs a good un.  :dremel:  You dont get a real sense of the red of the metal in the photos because of the flash but here you go.

  • Heated up the hammer until cherry red.
  • Dip in hardening compound.
  • Keep red hot for 5 mins minimum.
  • Quench in water.

















Its easy to do really.  I turned them around and did the skirt end of the hammer too as the trigger sears will rub along them during the cocking stroke and i don't want them to wear.  The hammers will be polished back up before use.

Cheers
Stot
« Last Edit: November 28, 2010, 09:43:59 AM by Stot »
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Offline Stot

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Update 11 - Hammer Tube End Cap
« Reply #43 on: November 28, 2010, 09:59:40 AM »
The Turning I have done was the hammer tube end caps.  These dont screw in, they are held in place by a bolt from underneath that also holds the trigger block on.  Basic slip fit caps really.

This is the penultimate bit of turning, last thing is to drill through the breech block for the barrel and bolt and then ill set the lathe up for milling.  :zap:

  • Chucked some brass stock the same as the valves were made from.
  • Turn down to slip fit the hammer tube.
  • Chamfer the edges and polish up a bit with wet and dry and some scotch brite pad.
  • Part off.
  • Mount the part in the lathe and face off to size.
  • Chamfer the back of the cap to taste. Polish this end.





















And a couple of pictures of all the parts so far.  :)





Cheers
Stot
« Last Edit: November 28, 2010, 10:01:11 AM by Stot »
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Offline cfellows

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Re: Building a Modern Pneumatic Airgun
« Reply #44 on: November 28, 2010, 10:36:18 AM »
Nice progress, Stot.  I'm particularly impressed with your finish on everything.  By they way, what kind of gloves are you wearing, and why?  Just wondered if that's something I should consider?

Chuck

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #45 on: November 28, 2010, 12:32:16 PM »
Hi Chuck,

Thanks for the comments.  Im trying to get these as A grade as I can just to see if I can.   I still have an A game gun out of the pair and the B game gun is filled with the first attempt parts.  Still its going to be a good standard. ;)

The gloves are just nitrite workshop gloves.  I've started wearing them when im working with brass.  It stops me getting splinters in my hands and they wont tear my hand off if they get caught on the chuck like normal gloves could..

Cheers
Stot
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Offline Spurry

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Re: Building a Modern Pneumatic Airgun
« Reply #46 on: November 28, 2010, 01:56:05 PM »
they wont tear my hand off if they get caught on the chuck



Are you sure?  My brother started wearing those when working. His usual MO when using a portable drill was to grip the revolving chuck to tighten and loosen the chuck. I do the same, but with bare hands. Luckily he broke only one of his fingers, as the extra grip provided by the glove rather took him by surprise. ::)

Pete

Offline j45on

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Re: Building a Modern Pneumatic Airgun
« Reply #47 on: November 28, 2010, 02:28:39 PM »
I use these as a mechanic and they will indeed fall apart very easily latex ones have more stretch and and will wrap around a drill or impact gun along with your hand
Jason

Offline Stot

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Re: Building a Modern Pneumatic Airgun
« Reply #48 on: November 28, 2010, 02:34:13 PM »
Yeah Like Jason says, the Nitrile ones have far less stretch before they tear.   I have to change mine a couple of times a session from just changing tools.

Cheers
Stot
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Offline Spurry

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Re: Building a Modern Pneumatic Airgun
« Reply #49 on: November 28, 2010, 06:48:32 PM »
Thanks both. Useful info to pass on.

Pete